Electric circuit arrangements for operating electric discharge lamps



Feb. 18, 1958 J. GATES 2,824,262

' ELECTRIC CIRCUIT ARRANGEMENTS FOR OPERATING ELECTRIC DISCHARGE LAMPS Filed July 26, 1951 2 Sheets-Sheet 1 Inventor":

Julius Gates,-

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Feb. 18, 1958 1 J. CATES 2,824,262

ELECTRIC CIRCUIT ARRANGEMENTS FOR OPERATING ELECTRIC DISCHARGE LAMPS Filed July 26, 195] 2 Sheets-Sheet- 2 Fig.5. 5

Inventor: Jud'ius Cates,

by P/W I IS Attorney.

ELECTRIC CIRCUIT ARRANGEMENTS FOR OPER- (ATING ELECTRIC DISCHARGE LAMPS Julius Cates, Weinbley, England, assignor to General Electric Company, a corporation of New York Application July 26, 1951, Serial No. 238,627

3 Claims. (Cl. 315 97) This invention relates to improvements in electric circuit arrangements for starting and operating electric discharge devices having pre-heatable electrodes. These circuits commonly include a filament heating transformer having secondary windings for the supply of heating current to the filamentary electrodes of one or more of said devices, the primary winding of the transformer being arranged for connection to a suitable source of supply, possibly in series with a ballast impedance, and connections extending between the primary winding and at least one pair of said secondary windings for the supply of operating voltage to the electrodes of a device, or devices in series, arranged to be connected between said pair of secondary windings, said connections possibly also or alternatively including a ballast impedance. In the case of a plurality of devices connected in series between a said pair of secondary windings, one or more further secondary windings are provided, not connected to the primary winding, for the supply of heating current to the further electrodes of the devices. More particularly, though not exclusively, the invention is concerned with electriccircuit arrangements of this kind for operating low pressure fluorescent electric discharge lamps.

In circuit arrangements of the kind referred to the primary and each said pair of secondary windings of the filament heating transformer have hitherto usually been arranged so that the total voltage available for the operation of the device or devices is the sum of the voltages developed across the secondary windings and the voltage appearing across the primary winding, so that the stepup of the primary voltage obtained in this way facilitates starting of the device or devices. Such step-up of the primary voltage, is, however, not always required to ensure reliable starting, and we have found that by a different arrangement of the primary and secondary windings a different advantage may be secured, namely that the load on the filament heating transformer is reduced, thus safeguarding the transformer and possibly enabling a smaller and cheaper transformer to be used.

According to the invention, in an electric circuit arrangement of the type specified, the windingsof at least one said pair of secondary windings connected to the primary winding of the filament heating transformer are directed so that in operation the voltages developed across them are in opposition to the voltage developed across the primary winding.

In this way it is arranged that the main discharge current flowing in operation of the arrangement, between the electrodes to which the said pair of secondary windings are connected does not flow through the secondary windings themselves, with consequent reduction in the loading of the transformer.

In the case where a circuit arrangement in accordance with the invention is arranged for the operation of a plurality of devices in parallel from the same filament heating transformer, preferably the windings of each said pair of secondary windings connected to the primary wind- ICC ing for the different parallel discharge paths are directed so that the voltages developed across them in operation are in opposition to the voltage developed across the primary winding.

The invention is of greatest utility in the case where the primary winding of the filament heating transformer is arranged to be connected directly across the supply, as is usually required in the case referred to in the preceding paragraph, since in such'arrangements the transformer must be rated for continuous operation at the supply Volt 7 age whereas inthe case where the ballast impedance is included in series with the primary winding across the supply, the voltage across the primary winding falls considerably as soon as the device or devices operated by it have started and the transformer can berated for continuous operation at 'a voltage lower than the supply voltage; a larger transformer is thus required in the former case and the arrangement in accordance with the invention helps to reduce this disadvantage.

Where an arrangement in accordance with the invention is used for operating a plurality of devices in series, the

said pair of secondary windings are connected to the electrodes at each end of the series-combination of lamps, and further secondary windings not connected to the primary winding are provided for heating the intermediate electrodes; such further secondary windings should all be connected so that the voltages developed across them are in the same direction, along the series of lamps, as the voltage across the primary winding.

The invention will be further described with reference to Figures 1 to 5 of the accompanying drawing which show, by way of example, different embodiments of it.

Figure 1 shows a circuit arrangement'for operating a. low pressure fluorescent electric discharge lamp, the lamp T being shown connected in position and having an earthed starting strip E.

In this arrangement the primary P of a filament heating transformer has its end terminals 1, 2 connected directly across the input terminals I 1 and has a pair of secondary windings S and S across the terminals of which are: connected the terminals of filamentary electrodes F and F of the lamp T.

One end terminal 5 of the secondary S is connected to the end terminal 1 of the primary P through a ballast impedance L, whilst one end terminal of the secondary S is connected directly to the end terminal 2 of the primary P, so that the lamp T is elfectively connected in series with the impedance L'across the primary P; the other end terminals of the secondaries S and S are denoted by 3 and 4 respectively. A radio interference suppression condenser C is shunted across the lamp."

In accordance with the invention the secondaries S and S are so directed in said transformer relative to its primary P that in operation the voltages developed across them are in opposition to the voltage developed across the primary, that is to say so that when '1 is negative with respect to 2, 3 and 5 are negative with respect to 2 and 4 respectively, and conversely when 1 is positive with respect to 2, 3 and 5 are positive wtih respect to 2 and 4 respectively.

In this way it is secured that the greatest voltage diff erence applied between the lamp electrodes appears between those ends of the electrodes connected directly to the primary of the filament heating transformer, i. e., not connected through the secondary windings, so that the flow of the main discharge curernt through the secondary windings is avoided and the total wattage dissipated in the transformer thereby reduced.

By way of illustration, for the operation of a 4 ft. 40 watt tubular fluorescent lamp, the transformer- P con.

P e e Feb-.1 .1 58.

sisted of a primary coil of 3860 turns of 42 S. W. G. wire wound on a shell type core whose central limb was "3 wide and long, each window width being while the depth of the iron stack was Each secondary winding consisted of 152 turns of 34 S. W. G. wire wound on top of the primary winding.

The ballast impedance consisted of a choke of impedance 380 ohms at 0.4 amp. on a 50 cycle supply.

When operating on a 220 volt 50 cycle supply, with the secondary windings connected in opposition to the primary winding as aforesaid, it was found that the steady current in each secondary winding before starting was about 0.3 amp. After starting the current fell to about 0.28 amp. while the current in the main discharge was 0.43 amp.

On reversing the polarity of connection of the secondary windings, by way of check, it was found that the current in each secondary winding after starting increased to 0.44 amp. whilst the main discharge current was 0.45 amp.

Figure 2 of the accompanying drawing shows an arrangement similar to that of Figure 1, with the same reference numerals denoting corresponding parts, in which the ballast impedance L is connected in series with the primary winding P across the input terminals; this arrangement has the known advantage that after starting of the lamp T the voltage across the primary P falls and so reduces the heating current supplied to the electrodes F and F which during operation are additionally heated by the discharge, thereby tending to maintain the heating of the electrodes constant. The secondary wind ings S and S are again in opposition to the primary winding P and the wattage dissipated in the transformer is less than it would be if S and S were wound in the same direction as the primary as in the known arrangements of this kind.

As already indicated the arrangement in accordance with the invention is not limited to the operation of a single discharge device, and Figures 3 and 4 show, by way of example, embodiments of the invention for operating two low pressure discharge lamps in parallel and series respectively.

Similarly it will be appreciated that the transformer may in some cases be auto-wound and in the latter case the step-up part of the main winding appears in series with the ballast impedance and the discharge device across the part of the main winding connected to the input terminals.

Also in some cases the ballast impedance may .be provided by the leakage reactanee of a stray field transformer; thus Figure 5 of the accompanying drawing shows by way of example, an arrangement using an autowound stray field transformer.

The ballast impedances used in circuit arrangements in accordance with the invention may, however, be of any suitable form, that is to say inductances, capacitances, resistances or any suitable combinations thereof, and in some cases may be provided by incandescent filament lamps the light from which might be usefully employed.

Referring now to Figure 3, the primary P of a filament heating transformer has its ends 1, 2 connected to the input terminals I and I The transformer has two pairs of secondary windings S S and S S across which are connected the electrodes F F and F R; of two low pressure fluorescent lamps T and T provided with carthed starting strips E and E respectively. Radio interference suppression condensers C and C are also provided.

One end 6 of the secondary S is connected to the end 1 of the primary winding through a ballast impedance L and 'one end 8 of the secondary S is connected to the said end 1 through a ballast impedance L one end of the secondary S and one end of the secondary 8;, are

connected directly to the end 2 of the primary winding P. The other ends of the secondaries S S S and S, are denoted by 3, 4, 5 and 7 respectively.

In accordance with the invention the secondary windings are so directed that when 1 is negative with respect to 2, 3 and 4 are negative with respect to 2, and 5 and 7 are positive with respect to 6 and 8 respectively.

In the arrangement shown in Figure 4 the primary P of the filament heating transformer has its ends 1, 2 connected to input terminals 1 I as before; there are now three secondary windings S S and S of which 8; has connected across it one electrode F of a first low pressure fluorescent lamp T 5 has connected across it one electrode E, 'of a second fluorescent lamp T whilst S has connected across it in series the remaining two electrodes F and F of these lamps. The lamps T and T are provided with earthed starting strips E and E respectively and radio interferences suppression condensers C and C are again shunted across the lamps.

One end 5 of the secondary S is connected through a ballast impedance L to the end 1 of the primary winding P whilst one end of the secondary S is connected directly to the end 2 of the primary winding; he other ends of S, and 5 are denoted by 3 and 4 respectively whilst the ends of the secondary S are denoted by 6 and '7.

In accordance with the invention, the windings S and S are so directed that when 1 is negative with respect to 2, 3 is negative with respect to 2 and 4 is positive with respect to 5.

The direction of the winding S is such that when 1 is negative with respect to 2, 6 is negative with respect to 7.

In the arrangement of Figure 5 the filament heating transformer is an auto-wound stray-field transformer the part P of the main winding (P, 5) being connected to the input terminals 3,, the transformer has two secondary windings S and 5 both associated with the part P of the main winding and having connected across them the electrodes F and F of a low pressure fluorescent lamp T provided with an earthed starting strip E. A radio interference suppression condenser C is shunted across the lamp.

One end 5 of the secondary S; is connected to the end 1 of the primary part P of the main winding through the step-up part S and one end of the secondary S is connected directly to the other end 2 of P.

The other ends of the secondaries S and S are denoted by 3 and 4 and the directions of the secondaries are such that when 1 is negative with respect to 2, 3 is negative with respect to 2, and 4 is positive with respect to 5.

it will be appreciated that one or both of the secondaries could alternatively have been associated with the step-up part S of the main winding, the point i then being taken as at the end of S away from P.

While I have described only certain preferred embodiments of my invention by way of illustration, many modifications will occur to those skilled in the art, and I therefore wish to have it understood that I intend in the appended claims to cover all such modifications as fall Within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electric circuit comprising a gaseous discharge lamp having a pair of thermionic filamentary electrodes, a transformer having a primary winding and a pair of secondary windings, said primary winding having a pair of input leads for connection to a source of alternating current, each said secondary Winding having a pair of output leads and being connected by said output leads immediately across a respective one of said filamentary electrodes. means connecting one of said output leads of each secondary winding to a respective one of said input leads. said secondary windings both being wound in voltage opposition to said primary winding, and impedance means in said circuit for ballasting said lamp.

2. An electric circuit comprising a pair of gaseous discharge lamps each having a pair of thermionic filamentary electrodes, a transformer having a primary winding and two pairs of secondary windings, said primary winding having a pair of input leads for connection to a source of alternating current, the secondary windings of one pair each having a pair of output leads and being connected by said output leads immediately across a respective one of the filamentary electrodes of diflerent lamps, means connecting one of the output leads of each secondary Winding in said one pair to the same one input lead, the secondary windings of the other pair each having a pair of output leads and being connected by said output leads across a respective other one of the filamentary electrodes of said lamps, means connecting one of the output leads of each secondary winding in said other pair to the same other input lead, all said secondary windings being wound in voltage opposition to said primary winding, and impedance means in said circuit for ballasting said lamps.

3. An electric circuit comprising a pair of gaseous discharge lamps each having first and second thermionic filamentary electrodes, means connecting the first electrodes of each lamp together to form a series connection of said lamps, a transformer having a primary winding and first, second and third secondary windings, said primary winding having a pair of input leads, said first and second secondary windings each having a pair of output leads and being connected by said output leads immediately across a respective second electrode of said lamps, means respectively connecting one output lead of said first and second secondary windings to different input leads, said first and second secondary windings being wound in voltage opposition to said primary winding, means connecting said third secondary winding across said serially connected first electrodes of both lamps, and impedance means in said circuit for ballasting said lamps.

References Cited in the file of this patent UNITED STATES PATENTS 1,980,534 Kirsten Nov. 13, 1934 2,264,055 Stocker Nov. 25, 1941 2,294,623 Lebrun Sept. 1, 1942 2,462,336 Ruff Feb. 22, 1949 2,558,293 Feinberg June 26, 1951 2,588,858 Lehmann Mar. 11, 1952 

